At present, secondary power sources are subdivided into a few types, according to materials that used for them, and running chemical reactions.
Secondary power sources (hereinafter also referred to as batteries) run on the principle of a summarized current-generating reaction. Energy is accumulated in a battery under charging from an external power source, because of a chemical reaction under discharge, the energy again directly turns into electrical energy and released to the external circuit. In addition, after the discharge the battery can again be charged by means of backward passage of current.
Following types of batteries are basic and the most used: the lead acid, the nickel-metal-hydride, the lithium-ion, and the lithium-polymeric.
Thus, lead dioxide (PbO2) and lead (Pb) are used as reagents; sulphuric acid solution is an electrolyte in lead batteries. Such batteries are used for supply of major power consumers, including production equipment, starting internal-combustion engines operation, emergency lighting systems, and uninterruptible power systems. Lead acid batteries have low-cost manufacturing and durability. Low specific energy, poor charge preservation, hydrogen loss, impossibility of storage in discharged state, problem with manufacturing of compact batteries should be reckoned among their deficiencies.
In nickel-metal-hydride batteries (Ni-MH), intermetallic semiconductor is an active material of negative electrode, reversibly sorbing hydrogen, i.e. the negative electrode is actually a hydrogen electrode, reduced hydrogen of which has the state of absorption. They're used for portable devices and hardware supply.
In lithium-ion batteries (Li-ion) carbonic material is used as negative electrode, into which lithium ions are reversibly penetrated. Lithium solution in a non-aqueous aprotic solvent is an electrolyte. Batteries have high specific energy, long life, and are able to operate at low temperatures. Due to big capacity, their output dramatically increased, and lithium-ion batteries have become one of the most prospective research trends on battery refinement. That particular type of batteries is used at mobile phones, notebooks, and other portable devices.
Lithium-polymeric batteries (Li-pol) have also become common use, in which carbonic material is used as the plate, into which lithium ions are reversibly penetrated. Vanadium, cobalt, and manganese are active materials for positive electrodes. Either lithium solution in non-aqueous aprotic solvents, enclosed in fine-pored polymeric matrix or a polymer (polyacrylonitrile, polymethyl methacrylate, polyvinylchloride, and others), plasticized by Lithium solution in an aprotic solvent (gel-polymeric electrolyte). Compared to lithium-ion batteries, lithium-polymeric batteries have higher capacity and are also used for portable electronic devices supply.
It should be mentioned that various chemical compositions are devised for electrodes, electrolytes, and membranes, and for every type of batteries. Completeness and speeds of running chemical reactions in batteries are conditioned by such materials, their compositions and structure.
With the lapse of time, major electrical and operational characteristics of batteries are changed because of irreversible processes, running within them, both under operation and at their storage.
The main task of development is improvement of electrical and operational characteristics of batteries.
Generally, ways of the improvement are determined by need for reducing of above mentioned irreversible processes efficiency on them.
Doping to major chemical composition of an electrolyte or an electrode is one of basic ways. Such doping makes it possible to block secondary processes or reduce their influence on major current-generating reactions running.
Thus, electrolyte doping (U.S. Pat. No. 5,962,164, 5 Oct. 1999; U.S. Pat. No. 5,780,183, 14 Jul. 1998; U.S.2003/0228525 A1, 11 Dec. 2003) is proposed to improve operational characteristics of lead-acid batteries. Such doping prevents alterations of electrodes paste, connected with intensive gassing and internal resistance growth at their sulfatation. Certain additives prevent sulfatation, formation of large crystals of lead sulfate that prevent running of reversible current-generating processes in full measure.
Polyacrylamide, an additive to electrolyte, content of which in electrolyte raises viscosity of electrolyte and keeps powdery pastes and resultants on electrodes surfaces (RU2257647, 27 Jul. 2005), is also used for improvement of alkali nickel batteries operational and electrical characteristics.
There's a certain metal-organic additive doped into a lithium-ion battery electrolyte, improving its operation stability and increasing the number of charge/discharge cycles (U.S. Pat. No. 7,217,477, 15 May 2007). The metal-organic additive makes it possible to escape excess voltage on electrodes, using insulating layer formation on cathode surface. The surface of a cathode active material is controlled by the additive; otherwise, side reactions with the electrolyte run on it. There are certain additives of carbonate type, doped into the lithium-ion battery electrolyte composition, making possible increasing the number of charge/discharge cycles and providing a battery operation both at room and lowered temperatures (EP1215746, 19 Jun. 2002).
Essentially, the purpose of above mentioned doping is to make it possible to run the current-generating reaction in full measure. Such additives can make possible batteries operation with characteristics that are extreme to their operating components materials (electrolyte and electrodes), and support the batteries operation under conditions, regulated by the types of batteries.